Conventionally, a controlled-release insect-controlling resin molded product has been obtained by the following steps: (i) kneading a saturation dissolution amount or more of a non-vaporizable insect-controlling component into a base resin; (ii) molding the resulting melt mixture into a desired shape; and (iii) gradually bleeding a supersaturation amount of the insect-controlling component onto a surface of the resulting molded product. It should be noted here that the term “non-vaporizable insect-controlling component” collectively means non-vaporizable bioactive components, such as an insecticidal or insect control compound and an insect-controlling compound, which are effective against animal parasites such as fleas and ticks. In the following, such a non-vaporizable insect-controlling component is sometimes referred to simply as “insect-controlling component”. The controlled-release insect-controlling resin molded product is widely known as an insect-controlling collar for protecting a dog, cat, etc. from fleas and ticks. The insect-controlling collar is commercially available as a hermetically-packaged product. Before use, the collar is taken out of the package and worn around the neck of the dog, cat, etc.
Such a controlled-release insect-controlling resin molded product has some manufacturing and functional problems. One of the manufacturing problems is concerned with ease of manufacturing control: Bleeding of the insect-controlling component kneaded into the base resin causes the base material surface to be sticky immediately after the molding, thus placing restrictions on time (lead time) from molding to hermetic packaging. Another manufacturing problem is associated with preservation stability: In a distribution process of the product after the hermetical packaging, the insect-controlling component bleeds in the package to cause the base material surface to be sticky by the time the package is opened. In the meantime, most important ones of the functional problems as a controlled-release insect-controlling resin molded product are problems in immediate effectiveness and residual effectiveness.
The term “immediate effectiveness” here means that it takes a short time for a controlled-release insect-controlling resin molded product to come to bring about its desired effect after it is brought into use by opening the package. The term “residual effectiveness” here means that the desired effect lasts over a long time from the start of use.
Further, the term “bleed” represents a phenomenon when a molded product retains a saturation dissolution amount (a supersaturation amount) or more of an insect-controlling component, an extra portion of the insect-controlling component (=Total Amount of Insect-controlling Component Contained in Molded Product−Saturation Dissolution Amount of Insect-controlling Component in Molded Product) moves onto a surface of the molded product.
An example of such a controlled-release insect-controlling resin molded product is disclosed in Patent Literature 1 (JP 2001-279033 A (published on Oct. 10, 2001)). Patent Literature 1 discloses: (i) a resin composition containing a polyolefin resin, an insecticidal compound, and aliphatic hydrocarbon; and (ii) a molded product made of the resin composition. Further, Patent Literature 2 (JP H9-77908 A (published on Mar. 25, 1997)) discloses: (i) a resin composition containing a base resin, an active compound such as an insecticide, and a vaporizable plasticizer; and (ii) a molded product made of the resin composition.
However, in either of the techniques disclosed in these Patent Literatures, when the base resin is a polyolefin resin such as a polyethylene resin and a polypropylene resin, the base resin is poor in flexibility. As such, these techniques are not applicable to the field of animal insect-controlling collar for animals, etc. required to be flexible.
Furthermore, even though these techniques can satisfy the aforementioned ease of manufacturing control and preservation stability to some degree, they are grossly deficient in immediate effectiveness and not necessarily satisfactory in long-term residual effectiveness, thus posing the most important functional problems as a controlled-release insect-controlling resin molded product. In fact, these techniques require such a long time as three days or more from the start of use of the product after opening until an effective amount of an insect-controlling component bleeds onto the base material surface. Moreover, after a long period of time has elapsed since the start of bleeding, a decrease in bleed amount causes a decrease in amount of the insect-controlling component on the base material surface.
In view of the above, it is conceivable to increase the amount of the insect-controlling component contained. However, even the increase merely causes a slight increase in bleed amount. It can hardly be said that such sufficient immediate effectiveness corresponding to the increase in amount of the insect-controlling component contained is obtained.